During emergency braking of a rail vehicle, a control system of the said vehicle applies spring actuated disc brakes and electromagnetic and/or permanent magnet track brakes (collectively referred to hereinafter as “the emergency brakes”) to achieve braking. The track brakes are designed to function in an on/off manner. The present control of these track brakes is realized by contactors to switch the track brakes on. At present, the brake force of the emergency brakes programmed into the control system is designed for the maximum vehicle weight. Consequently, the application of the emergency brakes on a vehicle which has less than maximum load, combined with the low rotational inertia of the wheels, leads to wheel slide and wheel flats. Presently existing systems apply the emergency brakes in coarse steps based on pre-calculated load conditions. Furthermore, the track brake friction increases at lower speeds, resulting in an abrupt stop causing an uncomfortable ride for the passengers.
In order to overcome the disadvantages of wheel slide, wheel flats, and abrupt stops; a two-level emergency brake (EB) system was introduced. The system uses a brake assurance monitor (BAM) to intercept the emergency brake command and control the emergency brakes as needed. In an EB level I braking situation, the BAM controls braking through the use of a linear induction motor (LIM) and track brakes in closed loop deceleration control without applying disc brakes, hence avoiding wheel flats and abrupt stops of the vehicle. In an EB Level II braking situation, the BAM monitors the achieved deceleration profile (from the EB Level I braking) and switches control to the emergency brakes if the required profile is not achieved, resulting in a full application of the disc and track brakes.
U.S. Pat. No. 4,835,693 (hereinafter Smith et al.) discloses a BAM for controlling the braking and propulsion systems of a vehicle comprising a controller for controlling three modes of vehicle braking, namely, normal braking, a first level emergency braking, and a second level emergency braking. The BAM provides emergency braking at two levels. In the first level emergency braking, the braking can be by means of track brakes and the propulsion system, (i.e., LIM) thus avoiding wheel flats and sudden stopping. When the first level emergency braking is not in accordance with a predetermined stopping profile, the controller switches the system to the second level emergency braking which relies on the wheel brakes and the track brakes.
While the BAM functions well, it adds equipment, and considerable additional car wiring. This, further, increases the cost of the system while adding to the complexity of the system. In view of the aforementioned disadvantages and problems with existing braking systems and brake monitors, it would be advantageous to have a braking system and method that provides for an improved and efficient control while providing a smoother ride for the passengers.